Camera with camera-shake detection apparatus

ABSTRACT

A camera wherein the light emitted by a subject, which has passed through a photographic optical system, is formed as an image on an area sensor, and which includes an electronic viewfinder that indicates the image of the subject based on the output from the area sensor and an apparatus that detects image shaking caused by camera shake, based on the output from the area sensor.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a camera which is equipped with an apparatusfor detecting camera shake and, more particularly, to a camera havingboth the above-mentioned shake-detecting apparatus and an electronicviewfinder which forms an image of the photo subject on an area sensorand displays the image based on the output from the sensor. It alsorelates to a camera containing the above-mentioned shake-detectingapparatus and a focus-detection apparatus.

2. Description of the Related Art

Cameras with an electronic finder have been previously published. Forexample, such a camera is disclosed in a Laid-Open Patent ApplicationSho 62-35329. However, this camera does not contain an apparatus whichdetects camera shake.

On the other hand, cameras with an electronic finder which can alsodetect camera shake have also been published. One example is found in aLaid-Open Patent Application Sho 63-129328. According to theapplication, the shake-detecting camera with an electronic findercontains a CCD area sensor for detection of camera shake, and detectscamera shake by comparing the image at one instant with that at anotherinstant. However, this camera does not use the TTL method.

Furthermore, video cameras containing a shake-correcting optical systemand an electronic finder have been published. One example is disclosedin Laid-Open Patent Application Sho 61-150581. In video cameras, thearea sensor is used for picture-taking, and the electronic finder isused to follow the subject. In the case of conventional video cameraswith a shake-correcting optical system, as in the one in the aboveapplication, camera shake is detected and corrected through an angularvelocity sensor.

One problem arising in connection with the above-given conventionalcameras is that the camera tends to become larger because it is equippednot only with an optical system and an area sensor for camera shakedetection, but also with an electronic viewfinder which also comprisesan optical system and an area sensor.

The camera in a Laid-Open Patent Application Sho 63-12932 describedabove does not include a shake-correcting optical system, and does notuse the TTL method; therefore, it is not able to confirm the desiredimage's correction region. In the case of a video camera with ashake-correcting optical system and an electronic finder, although theshake-corrected image is viewable in the finder, the camera shake in thepart of the camera where the image of the subject is formed cannot becorrected; consequently, the photo taken is blurred.

Moreover, because conventional cameras with an electronic finder and ashake-detecting apparatus do not use the TTL method, a parallax effectresults. As a result, it has been difficult to correct the shake.Further, since video cameras which use the TTL method are not stillcameras, it has not been necessary to consider the optical path.

On the other hand, while conventional auto-focus cameras contain afinder screen with a diffusing surface because the focal point isconfirmed on this screen, conventional shake-detecting cameras performthe same function using a beam of light passing through the finderscreen.

Where the finder screen has a diffusing surface, as in the case ofconventional cameras, one problem has been that the beam which shouldstrike the shake-detecting sensor becomes diffused and the lightintensity on the sensor surface decreases. Another problem has been thatthe roughness of the diffusing surface creates an image on the sensor,which reduces the precision of the shake-detecting capability. On theother hand, if the finder screen were made transparent, there would be adifferent problem: though the light intensity on the shake-detectingsensor would increase, it would no longer be possible to confirm thefocal point on the finder screen.

In addition, in order to perform detection and correction of imageshaking using the photo-image detecting method, it is necessary to havea separate optical path for detection as well as a separate optical pathfor auto-focusing, since these operations are both performed duringexposure.

One embodiment in which these two purposes are partly served by oneoptical path is published in a Laid-Open Patent Application Sho57-133414. In this application, the optical path for auto-focusing islocated just under the pentaprism, and images for shake detectionpurposes are produced through a half-mirror.

As explained above, in order to perform detection and correction ofcamera shake using the photo-image detecting method, it is necessary tohave a separate optical path for shake detection in addition to theoptical path for auto-focusing. Consequently, because of the necessityof having two different optical paths, compact cameras with thesecapabilities cannot be produced.

Further, in the case of the embodiment where the two purposes are partlyserved by one optical path, not much beam is available, since the areathat the half mirror can reflect is only a fraction of the finder'sfield of vision; subsequently, there has been a problem of insufficientlight.

SUMMARY OF THE INVENTION

The present invention was made in order to resolve the problemsdescribed above and provide a shake-detecting camera with an electronicfinder which does not contain two different area sensors for (1) camerashake detection and (2) a finder indicating the entire photo area, butinstead uses only one area sensor, which works on behalf of both thecamera shake detection apparatus and the finder.

It is also the purpose of this invention to provide a camera with anelectronic finder which allows photo-taking during automatic shakecorrection as well while the operator is visually confirming thecorrection.

It is also the purpose of this invention to provide a shake-detectingcamera with no parallax problems which can detect image shaking.

It is also the purpose of this invention to provide a shake-detectingand correcting camera which allows confirmation of the focal point onthe finder screen and can handle images of low light-intensity.

It is also the purpose of this invention to provide a compactshake-detecting camera which is not adversely affected by insufficientlight.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of the Main CPU, which comprises the centralcomponent of the shake-detecting camera with an electronic finderprovided by this invention;

FIGS. 2A through 2D are drawings explaining how the electronic finder ismounted to the camera body;

FIG. 3A illustrates the optical system of the shake-detecting camerawith an electronic finder provided by this invention;

FIG. 3B illustrates details of the driver of the shake-detecting opticalsystem;

FIGS. 4A through 4C show the screen of the electronic finder;

FIG. 5 illustrates a modified version of the optical system shown inFIG. 3A;

FIGS. 6A and 6B illustrates how the electronic finder is mounted in theembodiment shown in FIG. 5;

FIG. 7 is a block diagram of the camera shake detecting/correctionsystem;

FIG. 8 is a model diagram of the light receptacle of the CCD;

FIG. 9 is a drawing explaining correlative values for determining thedegree of camera shake;

FIG. 10 is a drawing explaining the method of interpolative calculation;

FIG. 11 is a drawing explaining how the correction lens is driven;

FIGS. 12A and 12B are circuit diagrams which illustrate the circuitscontrolling the CCD's integral time function;

FIG. 13 is a drawing illustrating changes in output from the LightMeasuring Circuit along a time axis; and,

FIGS. 14 through 16 are flow charts explaining the operations of theMain CPU and the Control CPU of the shake-detecting camera with anelectronic finder provided by this invention.

DESCRIPTION OF THE EMBODIMENTS

The embodiments of the present invention are explained below withreference to drawings. FIG. 1 is a block diagram which indicates themain part of the shake-detecting camera provided by this invention.

In FIG. 1, signals from photometric SPD (Silicon Photodiode) 2 are inputto Light Measuring Circuit 31. Light Measuring Circuit 31 calculates theoutput from SPD 2 and transmits the calculated result to Main CPU 1.Taking Lens 3 is removable and interchangeable. Aperture movement andfocusing are performed through Aperture Driving Circuit 4 and FocusingCircuit 5. In Lens Circuit 6 is saved the F-number for Taking Lens 3,focal length, and various parameters for shake correction. Further,Taking Lens Circuit 6 contains an actuator which drives theshake-correcting optical system and a control circuit.

Auto-Focus Mirror 7 reflects part of the light passing through TakingLens 3 to Focus Detecting Circuit 14. Auto-Focus Mirror 7 is retractedby Auto-Focus Mirror Driving Circuit 8 so as not to prevent the lightfrom reaching the film during film exposure. Shutter 9 is a focal planeshutter. It contains a front shutter and a rear shutter, and is drivenby Shutter Driving Circuit 10. Switch S1 turns on when the shutterrelease button is pressed to the first stage, and performs auto-focusingand photometric functions. Switch S2 turns on when the shutter releasebutton is pressed to the second stage. Film Winding Circuit 15 performswinding and rewinding of film. Switches S1' and S2' are shutter releasebuttons located in the remote finder, described below, and function inthe same manner as switches S1 and S2. Switch SC is a switch to operatethe continuous photo-taking mode.

Shake Detecting Optical System 40 and Electronic Finder Optical System41 are optical systems which transmit light to the shake-detecting CCD,described below, and are driven by Optical System Driving Circuit 42.When shake detection is performed, Shake Detecting Optical System 40 isemployed, and when display of the photo image is performed using theabove CCD, Electronic Finder Optical System 41 is used. Further, ShakeCorrecting Circuit 18, described below, is linked to the Main CPU forthe purpose of detecting camera shake. Shake Correcting Circuit 18communicates with Shake Detection/Correction Means 11.

Furthermore, Exposure Compensation Amount Input Means 22, which adjuststhe amount of exposure based on the photometric value, and ISODetermining Circuit 23, which determines film sensitivity, are linked tothe Main CPU.

Next, the electronic finder is explained below. FIGS. 2A through 2Dillustrate how the electronic finder is used. In FIG. 2A, ElectronicFinder 100, which can be pulled in an upward direction and detached, ismounted on the upper side of Camera Body 12. Electronic Finder 100includes LCD 63 for the display of the finder image and Shutter ReleaseButton 101. When Electronic Finder 100 is used as in FIG. 2A, it is usedas a waist level finder. FIG. 2B illustrates the camera with ElectronicFinder 100 pulled up towards the operator. The operator can see thefinder image without peering into the finder eyepiece. Therefore, it ispossible to take photos while holding the camera at the chest level orabove the head, confirming the photo image by observing the finderimage. FIG. 2C illustrates the camera with Electronic Finder 100 pulledup towards the front. This makes it possible for the operator to take aphoto with a self-timer while ensuring the desirability of the photoimage through the finder image. In this case, however, the image onFinder Image Indication LCD 63 is upside down.

FIG. 2D illustrates the camera when Electronic Finder 100 is detachedfrom Camera Body 12. With Electronic Finder Extension Cord 102, theoperator can take a photo at a distance from the camera by pressingShutter Release Button 101, while confirming the image quality byobserving the finder image in LCD 63.

Image signals to LCD 63 are received by Camera Shake Detection Sensor44's CCD Image-Sensing Unit 51, explained below with reference to FIG.7. The CCD exposure period at this time is determined in accordance withthe camera exposure. Therefore, an image shown on LCD 63 is essentiallysame as that of an image exposed on a film. When exposure compensationis performed during auto-exposure photographing. Exposure CompensationAmount Input Means 22 should be adjusted so that the area to which theoperator wants to adjust the exposure can be observed on LCD 63 withgood shade gradation. When setting the exposure during manual exposurephotographing, the aperture and shutter speed should be adjusted so thatthe area to which the operator wishes to adjust the exposure can beobserved on LCD 63 with good shade graduation as well. In addition, whenthe operator wishes to intentionally overexpose or underexpose thephoto, a picture with the intended exposure can be easily obtained ifthe exposure is determined by observing LCD 63.

FIG. 3A illustrates the optical system of the shake-detecting camerawith an electronic finder provided by this invention. In FIG. 3A, TakingLens 3 contains Shake Correction Lens 32 and Shake Correction Lens DriveUnit 33, which moves Shake Correction Lens 32. Since the details ofShake Correction Lens Drive Unit 33 are public knowledge, theirexplanation is omitted here. Inside Camera Body 12 is affixed PellicleMirror 34, which reflects part of the beam passing through Taking Lens 3towards the finder optical system, with the remaining beam passingthrough to Shutter 35. The part of the beam which passes throughPellicle Mirror 34 is reflected toward Focus Detection Module 36 bymeans of Auto-Focus Mirror 7. Auto-Focus Mirror 7 is retracted byAuto-Focus Mirror Driving Circuit 8 (not indicated in the FIG.) to aposition where it does not prevent the beam from reaching the filmduring film exposure.

The beam reflected by Pellicle Mirror 34 passes through Condenser Lens37 and enters Pentaprism 38. On one side of Eyepiece 39 of Pentaprism 38is located photometric SPD 2. Surface 38a of Pentaprism 38 is a halfmirror, which allows part of the beam to escape Pentaprism 38. Theescaping beam passes through Shake Detecting Optical System 40 andreaches Shake Detection Sensor 44 after being reflected by ReflectionMirror 43. Shake Detecting Optical System 40 and Electronic FinderOptical System 41 are driven by Optical System Driving Circuit 42, andare alternately driven in and out of the optical path. Shake DetectingOptical System 40 and Electronic Finder Optical System 41 respectivelyre-form the image on Finder Focal Plane 45, located on Shake DetectionSensor 44. Shake Detection Sensor 44 is a CCD area sensor. Pentaprism 38could be a hollow pentamirror containing air inside, instead of a glassblock.

Since the light from a photo subject is transmitted to the area sensor,i.e., Shake Detection Sensor 44, using Pellicle Mirror 34, as explainedabove, camera-shake detection can be performed by the photo-imagedetection method with a TTL camera. Further, since Pentaprism 38 is usedin the optical path to Shake Detection Sensor 44, a separate opticalpath to the sensor is not necessary.

FIG. 3B illustrates the details of Optical System Driving Circuit 42. Inthe Fig., Lens Holders 200 and 201, which secure Lens 40a of ShakeDetecting Optical System 40 and Lens 41a of Electronic Finder OpticalSystem 41, respectively, are affixed to Rotation Axle 205, which isconnected to Motor 210 by means of gears. The axis of Motor 210 moves inconjunction with Encoder Propeller 202 by means of gears, and therotation of Encoder Propeller 202 is monitored by Photo Coupler 203.On/off signals are generated every time the light between the two armsof Photo Coupler 203 is interrupted by the rotation of Encoder Propeller202. Controller 204 counts these pulse signals. Consequently, the numberof rotations of the rotation axis is monitored. By the turning on andoff of power to Motor 201 according to the monitored signals, Lens 40aof Shake Detecting Optical System 40 and Lens 41a of Electronic FinderOptical System 41 are rotated. Thus, Shake Detection Optical DrivingCircuit 42 switches the optical path from Shake Detecting Optical System40 to Electronic Finder Optical System 41 and vice versa.

As explained above, in this invention, the optical system to beprojected onto Shake Detection Sensor 44 is alternated by means ofOptical System Driving Circuit 42. As a result, the sensor image areaalternates between that used for the purpose of shake detection and thearea designated for focusing.

FIGS. 4A through 4C show the finder screen. The area indicated by (a) inFIGS. 4A and 4B is a transparent shake detection area. This area allowsthe amount of light to Sensor 44 to increase while the optical path tothe sensor is maintained. The area indicated by (c) is a matted area ofthe finder screen, where the light diffuses. In the same manner asconventional cameras, an image is formed in this area to detect thecorrect focal point. The area indicated by (a) is also employed toindicate the borders of the shake detection area. The area (b) in FIG.4A is the field of vision of the electronic finder. This area is alsotransparent so as to allow the amount of light reaching ElectronicFinder Optical System 41 to increase. FIG. 4C illustrates the case inwhich the entire area of the finder screen is transparent.

The image in area (a), part of the central region of finder screen (c),is projected onto the image-sensing surface by Shake Detecting OpticalSystem 40. This image is used by Shake Detection Sensor 44. Further,when Electronic Finder Optical System 41 is in use, almost the entirearea of finder screen (c) is projected on the image-sensing surface, andthis image is used by the electronic finder.

In FIG. 3A, Taking Lens 3 is mounted on Camera Body 12 by means of LensMount Unit 46, and is removable and interchangeable.

In the event that an ordinary non-shake-correcting lens is mounted onCamera Body 12, a warning is indicated on the finder screen whencamera-shake is detected. The warning may be displayed in written formon the electronic finder.

FIG. 5 illustrates another embodiment of this invention. In thisembodiment, Pentaprism 38, shown in FIG. 3A, is omitted. Since thisembodiment does not contain Pentaprism 38, the finder screen orCondenser Lens 37, the total cost may be reduced accordingly, and thecamera made lighter and more compact. In front of Shake Detection Sensor44' is located Image Re-forming Lens 45'. Small Area Relay Lens 40' andLarge Area Relay Lens 41' are alternately employed, thereby changing thebeam reaching area sensor 44. Located in the optical system of thisembodiment are Reflection Mirror 43 and Optical System Drive Actuator42'.

FIGS. 6A and 6B illustrate how the finder screen is used in conjunctionwith the optical system of this embodiment shown in FIG. 5. These figs.correspond to FIGS. 2A through 2D of the first embodiment. In FIGS. 6Aand 6B, Electronic Finder 63 is detachable.

Next, Shake Detection Correction Means 11 is explained with reference toFIG. 7. Shake Detection Sensor 44 contains CCD Image-Sensing Unit 51,Light Intensity Monitor 53, which controls the integral time of the CCD,and Light Measuring Circuit 54. Clock Generator 55 determines theintegral time of the CCD and the gain of the output amplifier bydetecting the output of Light Measuring Circuit 54. Clock Generator 55also generates a CCD drive clock and clocks for A/D Converter 61, D/AConverter 58, Sensitivity Correction Data Memory 59, and Dark CurrentCorrection Data Memory 60. The output of Shake Detection Sensor 44 isinput to A/D Converter 61 through Differential Amplifier 56 and GainControl Amplifier 57. Dark Current Correction Data Memory 60 andSensitivity Correction Data Memory 59 contain data regarding sensitivityvariations in the CCD and data for control of dark current which isoutput when the CCD receives no light. Dark Current Correction DataMemory 60 inputs data to D/A Converter 58. The D/A conversion outputsignals are input into the differential input of Differential Amplifier56. This controls the dark current of CCD 51. Gain Control Amplifier 57is an amplifier whose degree of amplification is controlled by digitalsignals. Gain Control Amplifier 57 is controlled by the sensitivityvariation data saved in Sensitivity Correction Data Memory 59, andcontrols sensitivity variations in the output of the CCD.

The output signals of the A/D Converter are saved in Image Memory 64,Basic Memory 65 or Reference Memory 66. Address Generator 67 generatesaddress data necessary for operation of Image Memory 64, Basic Memory 65and Reference Memory 66.

Calculation Circuit 68 contains Subtraction Circuit 69, Absolute ValueCircuit 70, Addition Circuit 71 and Register 72. The data of BasicMemory 65 and Reference Memory 66 are given as input.

Calculated results from Calculation Circuit 68 are saved in eitherCorrelation Memory 73, Vertical Contrast Memory 74 or HorizontalContrast Memory 75. These memories are linked to Control CPU 76 and canbe accessed from Control CPU 76. Control CPU 76 also controls AddressGenerator 67 and Clock Generator 55. Data in Image Memory 64 areconverted by D/A Converter 77 and input to Image Signal ProcessingCircuit 62. Switch SRV is a switch which turns "ON" when LCD 63, theelectronic finder, is pulled up towards the operator. When this switchis turned "ON", Image Signal Processing Circuit 62 turns the imagesupside down and displays them on LCD 63.

Next, the methods of camera shake detection and calculation of thedegree of the shake will be shown below. First, the sequence of shakedetection will be explained. In this invention, the subject image isdetected by Area Sensor 44, which can detect two-dimensional photo imagedata. The shake of the image is determined by detecting discrepanciesbetween the subject image at one time and that at another.

CCD 51 is an area sensor comprising I×J pixels. Basic Memory 65 andReference Memory 66 are I×J-word memories, while Correlation Memory 73is a memory with the capacity of H×H words. The photo-receptive surfaceof CCD 51 is divided into M×N blocks for the purpose of explanation.Each block consists of adjoining K×L pixels. Vertical Contrast Memory 74and Horizontal Contrast Memory 75 are memories with the capacity of M×Nwords.

The sequence of shake detection will be explained below. In thisexplanation, it is assumed that I=68, J=52, K=8, L=8, M=8, N=6 and H=5.The processing capability of A/D Converter 61 is 8 bits and that ofRegister 72 is 14 bits. One word in either Vertical Contrast Memory 74or Horizontal Contrast Memory 75 is indicated by 14 bits.

FIG. 8 is a model diagram of part of the photo-receptive area of CCD 51.In the fig., the pixel at bottom left is called P (1,1) while the pixelat top right is called P (68,52). Except for two rows of pixels on thecircumference, the photo-receptive area of CCD 51 is divided into blocksconsisting of 8×8 pixels. In the fig., the areas indicated by bold lineseach represent blocks. We will call the lower left block B (1,1) and theupper right block B (8,6).

The sequence of shake detection can be roughly divided into thefollowing three parts:

(1) Contrast calculation and selection of blocks

(2) Correlative calculation

(3) Interpolative calculation

Contrast calculation is performed for selection of blocks. Some parts ofthe subject whose image is formed on the photo-receptive unit of CCD 51are useful for shake detection, while others are not. In thisembodiment, contrast calculation is performed in order to select thoseparts suitable for shake detection. The contrast of the subject image ineach block is calculated and shake detection is performed using a totalof eight blocks, i.e., four blocks having high vertical contrast andfour blocks having high horizontal contrast.

(1) Contrast Calculation and Block Selection

First, the output of CCD 51 is saved in both Basic Memory 65 andReference Memory 66. Using this data, vertical contrast and horizontalcontrast are calculated for each block. The calculation is performed inthe order of horizontal contrast of Blocks (1,1), (2,1), etc., (7,6) and(8,6) and vertical contrast of Blocks (1,1), (2,1), etc., (7,6) and(8,6).

Assuming the output of P (i,j) of CCD 51 is A(i,j), the horizontalcontrast of B (k,l) is defined as ##EQU1## and the vertical contrast as##EQU2##

The sequence of the above calculation in the hardware illustrated inFIG. 7 is explained below. It is assumed that the content of BasicMemory 65, corresponding to the output data of P (i,j) of CCD 51, isR(i,j), and that of Reference Memory 66 is S(i,j).

First, Register 72 is cleared. Next, an address is sent from AddressGenerator 67 so that R(i,j) is given to one input terminal ofSubtraction Circuit 69 and S(i+1,j) to its other input terminal(provided, however, that i=8(k-1)+2, j=8(l-1)+2). The data calculated inSubtraction Circuit 69 are then input into Absolute Value Circuit 70 andabsolute values obtained. Then the data is added to the contents ofRegister 72 by Addition Circuit 71 and saved by Register 72. Then anaddress which will make i=i+1 is sent from Address Generator 67, and thesame calculation is performed. Thus, after processing is performedwithin the range where ##EQU3## is saved in Register 72.

The same content A(i,j) is saved in Basic Memory 65 and Reference Memory66, and since A(i,j)=R(i,j)=S(i,j), the contents of Register 72 equalhorizontal contrast: ##EQU4## When calculation of one block iscompleted, the contents of Register 72 are transferred to the partcorresponding to that block in Horizontal Contrast Memory 75 and saved.

In the same manner, the horizontal contrast of all remaining blocks iscalculated and saved in Horizontal Contrast Memory 75.

Next, vertical contrast is calculated. As in the case of horizontalcontrast, Register 72 is first of all cleared. Then, an address is sentfrom Address Generator 67 so that R(i,j) is given to one input terminalof Subtraction Circuit 69 and S(i,j+1) is given to the other inputterminal (provided, however, that i=8(k-1)+3, j=8(l-1)+2). Absolutevalues are then determined for the data processed in Subtraction Circuit69. This data then is added to the content of Register 72 and saved.Next, an address that will make i=i=1 is sent from Address Generator 67and calculation is performed in the same manner. Thus, processing isperformed within the range where i=8(k-1)+3˜8k+2,j=8(l-1)+2˜8l+2.Subsequently, ##EQU5## is saved in Register 72. SinceA(i,j)=R(i,j)=S(i,j), the contents of Register 72 equal verticalcontrast: ##EQU6## When calculation of one block is completed, thecontents of Register 72 are transferred to the part corresponding tothat block in Vertical Contrast Memory 74 and saved.

In the same manner, vertical contrast of all remaining blocks iscalculated and saved in Vertical Contrast Memory 74.

The Control CPU selects a block having the highest contrast, eitherhorizontal or vertical, using the data obtained in the above fashion.Then it selects a block having the second highest contrast in theopposite direction of the first selection (for example, if verticalcontrast is the first selection, horizontal contrast is the secondselection) from among the remaining blocks. In this manner, a total ofeight blocks are alternately selected (four blocks each for vertical andhorizontal contrast). The selected blocks are B1˜B8.

(2) Correlative Calculation

The data used for contrast calculation as standard image data remain inBasic Memory 65. New data is read out of CCD 51 in sequence, and eachtime new data is read out, it is written into Reference Memory 66 as areference image. Each time new data is written into Reference Memory 66,the standard image and the reference image are compared and any spatialdiscrepancy between the two is detected as image shake. The image shakeis calculated by correlative calculation and interpolative calculation,which will be explained below.

The correlative value of block Bk (k=1,2, . . . 8) is defined by thefollowing formula: ##EQU7## (i_(k),j_(k) means the smallest number ofpixels in Bk.)

In the case of l=m=0, the formula reads as follows: ##EQU8## This is thevalue to which one block's absolute value of the difference between thestandard image and reference image regarding data from the same pixelsis added.

In cases other than l=m=0, Ck(l,m) is a value to which one block'sabsolute value of the difference between the data of P (i,j) of thestandard image and the data of P (i+1, j+m) of the reference image. Thetotal of the correlative values of the eight blocks is ##EQU9##

One input terminal of Subtraction Circuit 69 is connected to BasicMemory 65 and the other input terminal is linked to Reference Memory 66.Therefore, an address determined by the Control CPU is sent from AddressGenerator 67 so that R(i,j) is input into one input terminal ofSubtraction Circuit 69 and S(i+1, j+m) are input into the other inputterminal, and the i and j data within a prescribed range are processed.Then, C(l,m) is obtained in Register 72. This data is transferred to aprescribed address of Correlation Memory 73 and saved. By repeating theabove process, changing the value for l and m, all correlative valuesC(l,m):(l,m=-2,-1,0,1,2) are obtained.

(3) Interpolative calculation

When the calculated correlative values C(l,m) are aligned with l on thehorizontal axis and m on the vertical axis, the following configurationis obtained:

    ______________________________________                                        C(-2,2)  C(-1,2)    C(0,2)    C(1,2) C(2,2)                                   C(-2,1)  C(-1,1)    C(0,1)    C(1,1) C(2,1)                                   C(-2,0)  C(-1,0)    C(0,0)    C(1,0) C(2,0)                                   C(-2,-1) C(-1,-1)   C(0,-1)   C(1,-1)                                                                              C(2,-1)                                  C(-2,-2) C(-1,-2)   C(0,-2)   C(1,-2)                                                                              C(2,-2)                                  ______________________________________                                    

When there is no discrepancy between the standard image and thereference image, C(0,0) is 0; the further C(l,m) is from the center, thelarger it becomes. If the reference image diverges from the standardimage by l_(o) to the right and m_(o) to the top, C(l_(o),m_(o)) is 0;the more it moves away from this value, the larger C(l,m) becomes.However, the discrepancy in terms of pixels is not always expressed by awhole number. In addition, since the speed of image shake is not fixed,the shake-caused blur on the standard image and that on the referenceimage may be different. Where the distribution of correlative valuesC(l,m) in such a case is represented by contour lines, a fig. resemblingFIG. 9 is the result.

In FIG. 9, though values are obtained only for the lattice points,contour lines are drawn on imagined values between those points. Thecloser to the center the contour line is, the smaller the values become.The center of the contour lines is Point MP on coordinate (x₀,y₀); herethe reference image diverges from the standard image by x₀ horizontallyand y₀ vertically.

Since values obtained via correlative calculation are those on thelattice points only, it is necessary to find the value for Point MPthrough interpolative calculation using the lattice point data.

The magnification of Shake Detecting Optical System 40, the pixel sizeof CCD 51, and the time needed to perform integration are set so thatPoint MP is -1.5<X₀, Y₀ <1.5, taking into consideration the actualdegree of camera shake.

The interpolative calculation performed after correlative calculation iscompleted will be explained below.

First of all, the smallest C(l,m) value, C(l₀, m₀) is found. Dependingon the relationship among the values of l₀, C(l₀₋₁,m₀) and C(l₀₊₁,m₀),there exist possible cases (a) through (h) as shown in FIG. 10.

Case (a)

It is determined that 0≦x₀ <1.

x₀ is the l coordinate of the intersecting point of Straight Line (i),connecting Point (-1, C(-1,m₀)) and Point (0, C(0,m₀)), and StraightLine (ii), connecting Point (1, C(1,m₀)) and Point (2, C(2,m₀)).##EQU10##

Case (b)

It is determined that 0<x₀ <1.

x₀ is the l coordinate of the intersecting point of Straight Line (i),connecting Point (-2, C(-2,m₀)) and Point (-1, C(-1,m₀)), and StraightLine (ii), connecting Point (0,C(0,m₀)) and Point (1, C(1,m₀)).##EQU11##

Case (c)

It is determined that 0<x₀ <1.

The rest is the same as in the case (a). ##EQU12##

Case (d)

It is determined that 1<x₀ <2.

x₀ is the l coordinate of the intersecting point of Straight Line (i),connecting Point (0, C(0,m₀)) and Point (1, C(1,m₀)), and Straight Line(ii), which passes through Point (2,C(2,m₀)) and inclines at the sameangle but in the opposite direction as Line (i). ##EQU13##

Case (e)

It is determined that -1≦x₀ <0.

The rest is the same as in case (b). ##EQU14##

Case (f)

It is determined that -2<x₀ <-1.

x₀ is the l coordinate of the intersecting point of Straight Line (ii),connecting Point (-1, C(-1,m₀)) and Point (0, C(10,m₀)), and StraightLine (i), which passes through Point (-2,C(-2,m₀)) and inclines at thesame angle but in the opposite direction as Line (ii). ##EQU15##

Cases (g) and (h)

It is determined that shake detection is impossible for the reason thatthe shake exceeds the largest imagined shake.

Given above is the procedure to find x₀, but y₀ can also be found in thesame manner.

Next, the Driving Circuit for Correction Lens 32, shown in FIG. 3A, willbe explained.

FIG. 11 is a drawing explaining the Driving Circuit for Correction Lens32. In this explanation, only the horizontal component of the imageshake is considered. In FIG. 11, the horizontal axis t represents timeand the vertical axis x represents the location of the image. Times t-₃,t-₂, t-₁, etc. represent the times when CCD 51 begins performingintegration, and times t-₃ ", t-₂ ", t-₁ ", etc. represent the timeswhen performance of integration is completed. Interval TI_(i) spent forperformance of integration is calculated as TI_(i) =t_(i) "-t_(i).

When the photo subject is illuminated by an AC light source, the timeinterval for performance of integration is changed so that the exposureof CCD 51 is kept at the same level. Therefore, the time interval forperformance varies.

The intervals between integration starting times t-₃, t-₂, t-₁, etc. areequal. Curved Line 301 represents the locus of the image on CCD 51 whenthere is image shake. When camera shake is not corrected by CorrectionLens 32, the image moves on this line. Since shake correction starts att=t₀, Curved Line 301 is drawn to pass through Point (t₀,0). Jagged Line302 represents the locus of Correction Lens 32. Dotted Line 303represents the locus of the image on CCD 51 when shake correction isperformed. Points P-₂, P-₁, P₀, etc. represent the average location ofthe image during the time period when integration is being performed,i.e., t-₃ ˜t-₃ ", t-₂ ˜t-₂ ", t-₁ ˜t-₁ ", and so on. CCD data processedby integration during the period t_(i) ˜t_(i) " are read out during theperiod t_(i+1) ˜t_(i+2), and are further calculated. Then P_(i), thelocation of the image, is found. Based on the data thus obtained,Correction Lens 32 begins to operate at t_(i+2).

In the following explanation, P-₂, P-₁, P₀, etc., X₁, X₂, X₃, etc., X₁', X₂ ', X₃ ', etc., X₁ ", X₂ ", X₃ ", etc. are used as the names ofpoints, but they also represent the values of the x coordinate.

In order to begin shake correction at t=t₀, it is necessary to find theshake velocity during the interval between t₀ and t₁. The shake velocityis determined from the change in location of the image between the mostrecent two points, and it is expected that the shake velocity duringinterval t₀ ˜t₁ is the same. The latest known location of the image atpoint t=t₀ is P-₁. Since the time between P-₂ and P-₁ is TS-(TI-₃₋TI-₂)/2, the predicted shake speed Vx₀ is ##EQU16## Therefore, the ShakeCorrection Optical System is operated at velocity Vx₀ during theinterval t₀ ˜t₁.

Next, the case when t=t₁ will be explained. Since Correction Lens 32 wasoperated at velocity Vx₀, it has now moved to the location X₀. Thelocation P₀ is known at this point, so that the predicted shake velocityduring the interval t₁ ˜t₂ may be obtained by the following calculation:##EQU17## Because velocity Vx₁ is obtained based on the latest data onthe location of the image, it may be considered to be more precise thanVx₀ as a predicted shake velocity during the interval t₀ ˜t₁. Therefore,prediction error ERx₁ is found through the following calculation:

    ERx.sub.1 =(Vx.sub.0- Vx.sub.1)·TS

From these values, the location of the image X₁ at t=t₁ is predicted bythe following formula: ##EQU18##

G is called the prediction coefficient, and FIG. 11 shows an examplewhere G=2. At this point Correction Lens 32 must be moved to the newlypredicted point X₁, for which action time interval t₁ ˜t₁ ' is needed.Since it is predicted that the image will move to the location X₁ 'during that time, Correction Lens 32 is moved to the location,

    X.sub.1 '=X.sub.1 +Vx.sub.1 ·(t.sub.1 '-t.sub.1)

and is operated at velocity Vx₁ during the interval t₁ '˜t₂.

Next, the case when t=t₂ will be explained. By this time, CorrectionLens 32 has moved to the location X₁ ", as expressed by

    X.sub.1 "=X.sub.1 +Vx.sub.1 ·TS

Since the location of P₁ is known at this point, the predicted shakevelocity during the interval t₂ ˜t₃ can be calculated as follows:##EQU19##

Vx₂ may be considered to be more precise than Vx₁ as a predicted shakevelocity during the interval t₁ ˜t₂. Therefore, prediction error ERx₂ iscalculated as follows:

    ERx.sub.2 =(Vx.sub.1 -Vx.sub.2)·TS

From these values, the location of the image X₂ at t=t₂ is predicted tobe: ##EQU20##

Now, Correction Lens 32 must be moved to the newly predicted point X₂,for which action the time interval t₂ ˜t₂ ' is needed. Since it ispredicted that during this interval the image will move to the locationX₂ ', Correction Lens 32 is moved to the location

    X.sub.2 '=X.sub.2 +Vx.sub.2 ·(t.sub.2 '-t.sub.2)

and is operated at velocity Vx₂ during the interval from t₂ '˜t₃.

Next, the case when t=t₃ will be explained. Now, Correction Lens 32 islocated at X₂ ", calculated by

    X.sub.2 "=X.sub.2 +Vx.sub.2 ·TS

Since the location of P₂ is known at this point, the predicted shakevelocity during t₃ ˜t₄ can be calculated as follows: ##EQU21##(Provided, however, that the interval t=t₁ ˜t=t₁ ' is disregarded.)

Since Vx₃ may be considered to be more precise than Vx₂ as a predictedshake velocity during the interval t₂ ˜t₃, prediction error ERx₃ isgiven by the following calculation:

    ERx.sub.3 =(Vx.sub.2 -Vx.sub.3)·TS

From these values, the location of the image X₃ at t=t₃ is predicted tobe: ##EQU22##

Now, Correction Lens 32 must be moved to the newly predicted point X₃,for which action the time interval t₃ ˜t₃ ' is needed. Since it ispredicted that the image will move to the location X₃ ', Correction Lens32 is moved to the location

    X.sub.3 '=X.sub.3 +Vx.sub.3 ·(t.sub.3 '-t.sub.3)

and is operated at velocity Vx₃ during the interval t₃ '˜t₄.

In the same manner, X₄, Vx₄, X₅, Vx₅, etc. are obtained and the shakecorrection optical system is operated.

In this embodiment, the prediction coefficient G was fixed. However, itmay be changed during the shake correction sequence depending how theshake detection is performed. If the prediction error value ER does notdecrease, or if the positive/negative value of the prediction errorER_(i) does not reverse after several shake correction operations, theprediction coefficient G may be increased. Also, in the event thepositive/negative value of the prediction error ER_(i) continues toalternate, prediction coefficient G may be reduced.

Referring to FIG. 11, the time interval TR from t_(O) to t_(z)represents the camera's exposure time. As is seen in the fig., the shakecorrection sequence is repeated several times during this exposureinterval TR. That means that shake correction is carried out not justonce or twice, but several times at least. Therefore, the actualcalculation of the degree of the shake, and the subsequent shakecorrection calculations, must be performed within a relatively shortperiod of time. Time intervals TI₃, TI₂, TI_(O), TI_(n), etc., spent forperformance of integration by the sensor to detect camera shake, mustalso be short. While the exposure time TR is of the order of 10 to 1000milliseconds, that of TI_(n) is only a few milliseconds. Unless thisrelationship is maintained, shake correction will be ineffective.

As explained above, in this invention, shake detection is performedusing the output data from an area sensor which detects the image of thephoto subject, and shake correction is carried out based on the detecteddegree of shake, as described above.

Next, the interface between interchangeable Lens 3 and Camera Body 12will be explained. From interchangeable Lens 3 is input its owninformation corrective magnification KBLX and KBLY (values correspondingto each focal length in case of zooming, calculated as follows):

    (Degree of movement of the image on the film)/(drive pulse).

Then, the drive pulse values Xi=degree of movement of the image X_(O)/corrective magnification KBLX, or Yi=degree of movement of the imageY_(O) /corrective magnification KBLY, are found.

The data necessary to perform the above-described lens operation,namely,

1) Direction X: positive or negative;

2) Operation velocity Vx_(i) ;

3) Drive pulse Xi;

4) Drive pulse Xi';

5) Direction Y: positive or negative;

6) Operation velocity Vy_(i) ;

7) Drive pulse Yi;

8) Drive pulse Yi'; and

9) Reset signal to return to the original position

are then output to the lens. Reset signal 9 is set only when the lens isto be returned to its original position which is center of driving rangeof Correction Lens 32, and Correction Lens 32 is returned to itsoriginal position only when this signal is sent.

Based on the input data, Correction Lens 32 is operated as describedabove. When undetectable data is output, the same data transmitted theprevious time is output.

Next, control of the time spent for performance of integration by CCD 51will be explained.

FIG. 12A illustrates a circuit to control the time for CCD 51'sperformance of integration, which includes a light-intensity monitoringSPD and a Light Measuring Circuit. The Light Measuring Circuit includesan integration circuit and a reset switch. The light-intensitymonitoring SPD is located in the vicinity of the image-sensing area ofCCD 51. Photoelectric current, output from the light-intensitymonitoring SPD, is processed by the integration circuit. The output ofthe integration circuit is proportional to the amount of light cominginto the light-intensity monitor during the performance of integration.

The light-intensity monitor and Light Measuring Circuit are employed inorder to keep the output of CCD 51 at the same level even when the photosubject is illuminated by an AC light source such as a fluorescent lamp.This is because the output would fluctuate each time if the time for CCD51's performance of integration were fixed when photographing a subjectilluminated by an AC light source. This will be explained in detailbelow.

In order to stabilize the output of CCD 51, the time for integrationmust be adjusted according to the light-intensity of the photo subject.In this embodiment, integration begins to be performed in the LightMeasuring Circuit at the same time as in CCD 51, and the degree ofexposure of CCD 51 is monitored via the output of the integrationcircuit.

FIG. 12B is a modified version of FIG. 12A.

Next, the operation of the integration time controlling circuits shownin FIGS. 12A and 12B where CCD 51 is used as a shake detection sensorwill be explained. The reset switch is turned "ON", resetting theintegration circuit. The electric load in the storage unit of the CCD iscleared. When CCD 51 begins to perform integration, the reset switch isturned "OFF", and the Light Measuring Circuit begins to performintegration.

FIG. 13 illustrates changes in output of the Light Measuring Circuitalong a time axis. The horizontal axis t represents time spent forintegration and the vertical axis I represents the amount of the outputof the Light Measuring Circuit. When the photo subject is illuminated byan AC light source, the output from the Light Measuring Circuit ascendsin a curved line as shown in the fig. The photometric output is comparedwith an appropriate standard I₀ and when the photometric output Ireaches I₀, the integration circuit is reset and CCD 51's performance ofintegration is discontinued. The output of CCD 51 is read out and it isdetermined whether or not the degree of exposure is appropriate. Whenthe degree of exposure is determined to be appropriate, the standard I₀is used for subsequent exposure. When it is determined to be notappropriate, the degree of exposure is multiplied, for example, by K, I₀×K becomes the new standard I₀, and subsequent exposures are performed.

Next, the operation of the integration time controlling circuits whereCCD 51 is used as an image-capturing element for the electronic finderwill be explained. Based on the output signal from Light MeasuringCircuit 31, the output signal from Exposure Compensation Amount InputMeans 22 and the signal from ISO Determining Circuit 23 are set atStandard I₀ (details of which will be explained in the Main CPU'ssequence step #70 in FIG. 14.)

Now, the camera sequence including the above-described shake detectionand control and remote finder will be explained based on the flow chartsfor the Main CPU and for the shake-correction Control CPU.

First, the sequence of Main CPU 1 will be explained. In FIG. 14, theMain CPU is on wait in the loop of Step #5 (hereinafter "Step" will beomitted). Namely, it is waiting in the loop of #5 for Switch S1 to turn"ON" by the first stroke of the shutter release button. When Switch S1turns "ON", the AF completion flag AFEF and signal are reset (#10), andnecessary circuits are switched "ON", including Light Measuring Circuit31, Auto-Focus Module 14 and Shake Correcting Circuit 18 (#15). Then thereset signal of Correction Lens 32 is output to Taking Lens 3 (#20), thetimer is started after being reset (#25), the lens data of Taking Lens 3is input (#30), and full-aperture metering is performed (#35).

In #40, it is determined whether the AF completion flag AFEF is 1; if itis 1, the program jumps to #65, and if it is not, it advances to #45. In#45, auto-focusing is performed. In #50, it is determined whether thecamera is in focus or not as a result of the auto-focusing in #45. If itis in focus, the program goes to #55, and if not, it is diverted to #60.In #60, after Taking Lens 3 is moved to the focal point, the programjumps back to #45.

In #55, the AF completion flag AFEF becomes 1.

In #65, auto-exposure calculations are performed based on thephotometric information obtained in #35, as well as on the filmsensitivity and the distance information obtained as a result of theauto-focusing in #45. In #70, the exposure value for CCD 51 is set.

In #75, it is determined whether Switch S2, which is turned "ON" by thesecond stroke of the shutter release button, is "ON". If it is "ON", theprogram goes to #105, and if it is not, it is diverted to #80. In #80,it is determined whether Switch S1 is "ON". If it is "ON", the programjumps back to #25. If it is not "ON", it means the shutter releasebutton has not been pressed; therefore, it is determined in #85 by atimer whether a prescribed interval has elapsed. If such interval haselapsed, the program jumps back to #5, the waiting stage, after turning"OFF" (#100) certain circuits * including Light Measuring Circuit 3,Auto-Focus Module 14 and Shake Correcting Circuit 18. If the intervalhas not elapsed, the AF completion flag AFEF is set to 0 (#90), and theprogram advances to #80.

In #105, since the second stroke of the shutter release button ispressed, the release signal becomes an "H" level signal, which fact isthen transmitted to the Control CPU. In #110, the aperture of TakingLens 3 is stopped down to the level obtained in the auto-exposurecalculation in #65. Switchover occurs from Electronic Finder OpticalSystem 41 to Shake Detecting Optical System 40 (#115), the shakedetection signal becomes an "H" level signal, and the shake detectionsequence of the Control CPU commences (#120). Auto-Focus Mirror 7 isretracted (#125), stop-down metering for measuring light passed throughan aperture stopped-down is performed (#130), and the shutter speed iscorrected according to the auto-exposure calculations (#135).

In #140, the program waits for the exposure permission signal from theControl CPU to reach "H" level. When the signal reaches "H" level,Shutter 9 is released, and exposure control is performed (#145). Whenthe exposure is completed, reset signal is output to Taking Lens 3(#150), Correction Lens 32 is returned to the original position, theshake detection signal becomes an "L" level signal, and the Control CPUis informed that the exposure is complete (#155).

Film winding is performed (#160), and it is determined whether thecamera is in continuous photo mode (#165). If it is not in continuousphoto mode, the program diverts to #180; if it is in continuous photomode, the program goes to #170 and it is determined whether Switch S2 is"ON". If Switch S2 is "OFF", the program diverts to #180 becausecontinuous photographing is not available, even if the camera is incontinuous photo mode. If Switch S2 is "ON", the camera performscontinuous photographing; therefore, the shake detection signal becomesan "H" level signal (#175) and the program jumps back to #130.

Subsequently, Auto-Focus Mirror 7 is returned to the auto-focusing point(#180), the aperture of Taking Lens 3 is opened (#185), and the releasesignal becomes "L" level (#190), which fact is transmitted to ControlCPU 1. Switchover then occurs from Shake Detecting Optical System 40 toElectronic Finder Optical System 41 (#200). Then the program waits forS2 to turn "OFF" (#205), and it jumps back to #80 to be ready for thenext photo-taking.

Next, the operation of the Control CPU will be explained with referenceto FIG. 15. In #15 in FIG. 14, Shake Correcting Circuit 18 is turned"ON", starting the sequence. The flag and output signals are reset(#85), and CCD 51 starts performing integration after reset (#B10). Whenthe integration is completed in #B15, the data read out from thecalculation is dumped in Image Memory 64. (#B20). The dumped data isread out in sequence and D/A conversion occurs. Then the image isdisplayed on LCD 63 by Image Signal Processing Circuit 62. In #B25,after the integration of CCD 51 is reset, integration starts and theprogram jumps back to #B15.

When integration is not completed in #B15, the program is diverted to#B30. In #B30, the release signal from the Main CPU is checked; if it isin "H" level, the program advances to #B35, and if it is in "L" level,the program diverts to #B15. In #B35, the program waits until #B35 theshake detection signal from the Main CPU becomes "H" level before shakedetection begins.

When the shake detection signal becomes "H" level, performance ofintegration is begun after reset of integration in the CCD 51 (#B40). Atthis point, the Main CPU has already switched the optical system toShake Detecting Optical System. In #B45, the program waits for CCD 51 tocomplete the performance of integration. After the CCD 51 has completedperformance of integration, the data read out from the calculation isdumped to Basic Memory 65 and Reference Memory 66 (#B50). After CCD 51'sintegration is reset, integration is begun (#55).

Contrast calculation is performed (#B60) and blocks to be used for shakedetection are selected (#B65). The program waits for CCD 51 to completeintegration (#B70). When the integration is completed, data read out ofthe calculation is dumped to Reference Memory 66 (#B75), and after CCD51's integration is reset, integration is begun.

Correlative calculation (#B85) and interpolative calculation (#B90) areperformed, and the degree of image shake is detected. Lens data fromTaking Lens 3 are read out (#B95) and the degree and direction of shakefor shake correction by Correction Lens 32 is calculated (#B100).

In #B105, it is determined whether the shake detection signal from MainCPU is in "L" level; if it is in "L" level, the program diverts to #B130because shake detection is completed, and if it not in "L" level, theprogram advances to #B110 because shake detection continues. Theexposure permission signal becomes "H" level (#B110), informing the MainCPU that exposure can be begun, lens control data is output to TakingLens 3 (#B120), and the program jumps back to #B70.

In #B130, it is determined whether the release signal from Main CPU isin "L" level or not; if it is in "L" level, the program jumps back to#B10 because the photographing process is completed, and if it is not in"L" level, the program advances to #B135, because continuousphotographing is taking place, and it waits for the detection signal tobecome "H" level. When the detection signal becomes "H" level, theprogram jumps back to #B40.

FIG. 16 illustrates another embodiment of the Control CPU. Even afterrelease has begun, data is dumped to the image memory in #B247 and #B275and shake detection image information is displayed. In other words, theentire photo area is displayed on LCD 63 until just before exposurebegins; after exposure commences, system switchover occurs and the shakedetection area is displayed on the LCD.

Although the present invention has been described and illustrated indetail, it is clearly understood that the same is by way of illustrationand example only and is not to be taken by way of limitation, the spiritand scope of the present invention being limited only by the terms ofthe appended claims.

What is claimed is:
 1. A camera system comprising:an interchangeablelens for forming a photo image of a subject; a mirror for reflecting alight through the interchangeable lens; a finder screen on which a photoimage of the reflected light is formed, said finder screen having atransparent area; a sensor for transforming the light through thetransparent area of the finder screen into electric signals; means fordetecting the relative camera shake between the camera and the subject,based on the signals from the sensor; and a finder optical system forguiding the photo image on said finder screen to a photographer.
 2. Acamera system as stated in claim 1, wherein said sensor is an areasensor.
 3. A camera system as stated in claim 1, wherein said finderoptical system has a pentagonal prism, one of the reflecting faces ofthe pentagonal prism is translucent, and said sensor is located behindthe translucent face.
 4. A camera system as stated in claim 1, whereinsaid mirror is a pellicle mirror.
 5. A camera system as stated in claim1, further comprising means for correcting the relative camera shakebased on the amount of camera shake detected by said shake detectingmeans, and the shake correcting means is located in said interchangeablelens.
 6. A camera system as stated in claim 5, wherein said shakedetecting means is located in camera body, and data of camera shakedetected by said shake detecting means is transmitted from the camerabody to the interchangeable lens.
 7. A camera system as stated in claim1, wherein the camera uses a silver salt film.
 8. A camera systemcomprising:an interchangeable lens for forming a photo image of asubject; a mirror for reflecting a light through the interchangeablelens; a finder screen on which a photo image of the reflected light isformed, said finder screen having a transparent area; a sensor fortransforming a light passing through the transparent area of the finderscreen into electric signals; a pentagonal prism for guiding the imageformed on said finder screen to a photographer and for guiding the lightpassing through the transparent area to said sensor; and means forprocessing the signals from the sensor.
 9. A camera system as stated inclaim 8, wherein said sensor is an area sensor.
 10. A camera as statedin claim 8, wherein one of the reflecting faces of said pentagonal prismis translucent, and said sensor is located behind the translucent face.11. A camera system as stated in claim 8, wherein said mirror is apellicle mirror.
 12. A camera system comprising:a phototaking lens forforming a photo image of a subject; a mirror for reflecting a lightthrough the phototaking lens; a finder screen on which the photo imageof the reflected light is formed; image erecting means composed ofseveral reflecting faces for erecting the photo image on said finderscreen, wherein one of the reflecting faces is translucent; a sensor,located behind the translucent face of the image erecting means, fortransforming a light into electric signals; and means for detecting therelative camera shake between the camera and the subject, based on thesignals from the sensor.
 13. A camera system as stated in claim 12,wherein said image erecting means is a pentagonal prism.
 14. A camerasystem as stated in claim 12, further comprising means for correctingthe relative camera shake based on the amount of camera shake detectedby said shake detecting means, said shake correcting means being locatedin said interchangeable lens.
 15. A camera system as stated in claim 12,wherein said translucent face of the image erecting means reflects lighttoward a photographer.
 16. A camera system as stated in claim 12,further comprising a reforming lens for forming the photo image on thesensor, said reforming lens being located between the image erectingmeans and the sensor.
 17. A camera system as stated in claim 12, whereinsaid mirror is a pellicle mirror.
 18. A camera system comprising:aphototaking lens for forming a photo image of a subject; a mirror forreflecting a light through the phototaking lens; a finder screen onwhich the photo image of the reflected light is formed; image erectingmeans composed of several reflecting faces for erecting the photo imageon said finder screen, wherein one of the reflecting faces istranslucent; a sensor, located behind the translucent face of the imageerecting means, for transforming a light into electric signals; andmeans for processing the signals from the sensor.
 19. A camera system asstated in claim 18, wherein said image erecting means is a pentagonalprism.
 20. A camera system as stated in claim 18, wherein said sensor isan area sensor.
 21. A camera system as stated in claim 18, wherein saidmirror is a pellicle mirror.
 22. A camera system comprising:aphototaking lens for forming a photo image of a subject; a sensor fortransforming a light through the phototaking lens into electric signals;a switching optical system, located between the phototaking lens and thesensor, for switching image sensing fields of the sensor between firstfield and second field; first processing means for processing thesignals from the sensor when the first field is selected; and secondprocessing means for processing the signals from the sensor when thesecond field is selected.
 23. A camera system as stated in claim 22,further comprising an optical system composed of a mirror, a finderscreen, and a pentagonal prism between the phototaking lens and thesensor.
 24. A camera system as stated in claim 22, wherein said sensoris an area sensor.
 25. A camera system as stated in claim 24, whereinsaid first processing means detects the relative camera shake betweenthe camera and the subject.
 26. A camera as stated in claim 24, furthercomprising an electric view finder, wherein said second processing meansprocesses the signals so as to display the photo image on the electricview finder.
 27. A camera system as stated in claim 22, wherein thecamera uses a silver salt film.
 28. A camera system comprising:aphototaking lens for forming a photo image of a subject; a sensor fortransforming a light through the phototaking lens into electric signals;a switching optical system, located between the phototaking lens and thesensor, for switching image sensing fields of the sensor between firstfield and second field; and processing means for processing the signalsfrom the sensor.
 29. A camera system using a silver salt filmcomprising:a phototaking lens for forming a photo image of a subject; amirror for reflecting a light through the phototaking lens; a finderscreen on which a photo image of the reflected light is formed; apentagonal prism for guiding the photo image on the finder screen to aphotographer; a sensor for transforming a light into electric signals;switching means for switching image sensing fields of the sensor betweenfirst field and second field; first processing means for processing thesignals from the sensor when the first field is selected; and secondprocessing means for processing the signals from the sensor when thesecond field is selected.
 30. A camera system comprising:aninterchangeable lens for forming a photo image of a subject; a mirrorfor reflecting a light through the interchangeable lens, wherein areflecting face of said mirror has a transparent area; means fordetecting the relative camera shake between the camera and the subjectbased on a light reflected by the mirror; and means for detecting afocus condition based on a light passing through the mirror.
 31. Acamera system as stated in claim 30, further comprising means forcorrecting the relative camera shake based on the amount of camera shakedetected by said shake detecting means, and the shake correcting meansis located in said interchangeable lens.
 32. A camera system as statedin claim 30, wherein the camera uses a silver salt film.
 33. A camerasystem comprising:a phototaking lens for forming a photo image of asubject; a sensor for transforming a light through the phototaking lensinto electric signals; first switch for beginning phototakingpreparations; second switch for beginning exposure operation; means fordetecting the relative camera shake between the camera and the subject,wherein said shake detecting means begins detecting in response to thesecond switch turning on; and means for correcting the relative camerashake based on the amount of camera shake detected by said shakedetecting means.
 34. A camera system as stated in claim 33, wherein theelectric signals from the sensor are used in other processing than shakedetecting until the second switch turns on.
 35. A camera systemcomprising:a phototaking lens for forming a photo image of a subject; asensor for transforming a light through the phototaking lens intoelectric signals; first switch for beginning phototaking preparations;second switch for beginning exposure operation; an optical system forguiding the light through the phototaking lens to both the sensor and afilm during exposure operation; first processing means for conductingfirst processing of the signals from the sensor, in response to thefirst switch turning on; and second processing means for conductingsecond processing of the signals from the sensor, in response to thesecond switch turning on, wherein said second processing is differentfrom the first processing.
 36. A camera system comprising:a phototakinglens for forming a photo image of a subject; a sensor for transforminglight through the phototaking lens into electric signals; first switchfor beginning phototaking preparations; second switch for beginningexposure operation; means for detecting the relative camera shakebetween the camera and the subject based on the signals from the sensorin response to the second switch turning on; means for correcting therelative camera shake based on the amount of camera shake detected bysaid shake detecting means; and permitting means for permitting exposureoperation when the amount of camera shake is detected by the detectingmeans.
 37. A camera system comprising:a phototaking lens for forming aphoto image of a subject; a sensor for transforming a light through thephototaking lens into electric signals; first switch for beginningphototaking operations; second switch for beginning exposure operation;means for detecting the relative camera shake between the camera and thesubject, wherein said shake detecting means begins detecting in responseto the second switch turning on; means for correcting the relativecamera shake based on the amount of camera shake detected by said shakedetecting means; and means for stopping the shake correcting operationat the end of the exposure operation.
 38. A camera system as stated inclaim 37, further comprising means for winding a film after the shakecorrecting operation stopped.
 39. A camera system as stated in claim 37,wherein said shake correcting means begins correcting operation againwhen the next phototaking operation begins continuously.
 40. A camerasystem comprising:an interchangeable lens for forming a photo image of asubject; a pellicle mirror for dividing a light through theinterchangeable lens; a switch for beginning exposure operation; meansfor detecting the relative camera shake between the camera and thesubject based on a light reflected by the pellicle mirror during theexposure operation; and means for correcting the relative camera shakebased on the amount of camera shake detected by said shake detectingmeans.
 41. A camera system as stated in claim 40, wherein the shakecorrecting means is located in said interchangeable lens.